Older adults respond less predictably than younger adults to most medications, typically requiring lower daily doses to achieve desired therapeutic effects and minimize adverse effects and toxicity. This unpredictability is particularly evident among the frail elderly, who are at the upper extreme of the life cycle and often suffer from central neurodegenerative disorders and/or a significant burden of comorbid medical problems. Yet this population has a burgeoning need for clinical services and in recent years has become an increasingly important focus of attention among practitioners. The goal of this review is to provide clinicians with a conceptual framework for understanding and responding to aging and age-related events that influence pharmacotherapeutics in older patients with behavioral disorders. Limitations and gaps in our knowledge base are also highlighted. The article includes a phenomenological overview of the aging process, a consideration of age-related factors that influence the pharmacokinetic and pharmacodynamic properties of psychotropic drugs, and suggested methods of enhancing medication compliance.